The invention relates to a method and an apparatus for generating at least one section of a virtual 3D model of a body interior, in particular a hollow organ.
Such a method and such an apparatus are generally applied and/or used in the endoscopic examination of body interiors in the human or animal body. Such a body interior can be, for example, the bladder, the lung, the stomach, the throat, the esophagus, etc.
Without restriction of generality, the present invention is described with reference to the specific application of the examination of the bladder.
In the endoscopic examination of the bladder, the examining doctor attempts to acquire the organ with the endoscope in a fashion covering the area as much as possible, that is to say to “scan” it. It is important in this case that each part of the surface of the bladder is actually acquired or is acquired with adequate care. Whether each part of the surface of the bladder is acquired depends substantially on the experience of the doctor. However, it can occur that regions of the wall of the bladder are overlooked, that is to say are not endoscopically acquired. If the nonacquired regions of the wall of the bladder are, if appropriate, malign tissue areas, this can have serious consequences for the patient.
One reason why omissions of tissue areas or surface areas of the bladder come about during the endoscopic examination of the bladder is that the orientation of the doctor in the substantially spherical interior of the bladder is rendered difficult by the restricted field of view of an endoscope. To be specific, the restricted field of view of an endoscope has the consequence that one and the same endoscopic image cannot acquire the entire surface of the body interior, but only a specific surface area.
Moreover, since the endoscopic image visually displayed on a monitor has no spatial depth but, only a “two-dimensional” effect, it is not possible solely with the aid of the acquired endoscopic image to judge the surface area from which this endoscopic image originates. If, for example, a number of endoscopic images of different surface areas of the body interior are acquired and documented, and if a pathological finding is recorded on one of the endoscopic images, it is no longer possible later on to use the endoscopic images to determine unambiguously from which surface area this endoscopic image with the pathological finding originates.
Thus, it is also difficult for tissue regions treated in previous examinations to be found again in a repeated endoscopic examination, for example when monitoring the course of therapy or conducting tumor aftercare. Here, as well, the doctor is dependent on the quality of the documented findings. Because of the great similarity of the appearance of various surface regions of the inner wall of the bladder on the respective endoscopic image, reliably and quickly refinding a specific surface area of the body interior with adequate reliability is impossible, or possible only conditionally.
There is thus a need to acquire and document images of a body interior in a way that offers improved orientation of the doctor during examination of the body interior and, above all, a possibility for the doctor to establish which surface areas have already been examined and which have not yet been examined. In other words, it is desirable to give the examining doctor a means for navigating the endoscope in the body interior such that he can move the endoscope in the body interior in a targeted fashion so that it is possible for the surface of the body interior to be acquired endoscopically as quickly and completely as possible and documented.
The prior art has already described methods and apparatuses, for example in the document DE 197 50 698 A1, with the aid of which a body interior can be measured in three dimensions in order to generate a virtual model, that is to say a computer model, of the body interior. Described for this purpose in the said document is a plug-on unit for a flexible endoscope into which a probe can be inserted that contains an ordered optical fiber bundle with a cladding. The cladding is provided with equidistant markings that can be acquired with the aid of contactless scanning or readout means. The optical fiber bundle Is assigned an optical imaging means, the optical fiber end being assigned a beam deflecting means that permits the light beam to be deflected at right angles on all sides onto the surface of the measured body interior.
The document U.S. Pat. No. 5,704,897 describes an apparatus and a method that enables an optical display of an endoscopic image to be overlaid with a data field in order to support the navigation of an instrument during endoscopic operations. An endoscopic image is acquired with the aid of an endoscope and displayed on a display screen. Arranged on the endoscope is a position acquisition system the purpose of which is the permanent acquisition of the spatial position of the endoscope. The spatial data field, which forms a model of the body interior, is obtained by means of computed tomography, magnetic resonance tomography or ultrasound, and assigned to a human body in a specific position. A sensor that can be fastened on the patient's body serves the purpose of compensating movements of the body. A computer is used to bring selected points of the data field into agreement with corresponding points of the optical display by displacing specific points of the data field while the latter are superposed on the optical display.
A further document that is concerned with the documentation of courses of treatment is the document DE 297 23 333 U1, which discloses a system for refinding specific locations in a body cavity. This system has a tube for insertion into the body cavity, and an endoscope for optical display of the tissue surfaces surrounding the tube, the tube being at least partially of transparent design and having in its transparent sections optical markings that are aligned reproducibly relative to the patient, such that specific regions of the tissue surface are to be assigned to specific markings, and the specific regions can be refound with the aid of the assignment.
However, all the previously described known methods and apparatuses have the disadvantage that the endoscope is navigated only with the aid of a model specified in advance by an extracorporeal method, but in some circumstances this does not ensure an exact correlation between the respective endoscopy image of a surface area of the body interior and the associated area of the model, and so the disadvantage continues to exist of the risk that specific regions of the body interior can remain out of account during an endoscopic examination.